Dieter Roth: the video-diary Rembrandt

Dieter Roth chronicled the stuff of life with a poetic, sarcastic eye. He also filmed his death in meticulous, heartbreaking detail. Jonathan Jones on the standout show of this year's Edinburgh art festival

Dieter Roth sits at his desk, wearing a silk dressing gown and a soft cap. A lamp casts a warm glow as he studies a sheet of paper in front of him. Elsewhere, on another screen, we see the German-born artist watering his plants. He turns the camera so that it catches him walking outdoors where, in pallid sunlight, he pours nutrient-enriched water into a watering can. Soon he will be dead.

Dieter Roth made Solo Scenes in 1998, the final year of his life, thanks to an illness caused by alcoholism. At this time of all times, he chose to put himself under surveillance by setting up cameras throughout his house and studios in Germany, Switzerland and Iceland, filming himself going about his daily activities. On screen after screen, 128 in all, the sick artist, born in 1930, draws, makes notes, and just sits at his desk thinking. He looks busy, but it is hard to tell if he is creating new works or simply cataloguing old ones. Cameras catch him pottering about, even sitting on the toilet. Again and again, Roth's face peers in concentration at his work. His body in the dressing gown is large, his beard noble.

Roth must have known he looked like old Rembrandt in his farewell video. The anglepoise lamps that light his nocturnal labours give him the twilight colours of Rembrandt's kindly brush. Roth bows out with dignity, even when we see him on the loo – because, even there, he is reading, thinking.

What would you do if you had a year to live? Roth worked on. In almost every scene, he is intent on his art. Even when he is not producing, he is thinking about producing. Thinking, thinking. It is his dedication and his seriousness that come across. Once you know what he was facing, this autumnal kaleidoscope of flickering screens becomes an emotional tidal wave. Solo Scenes is about what we do in the face of death – and what Roth does is insist on life. From scribbling on a pad to caring for his plants, he clings to its everyday beauty.

People video themselves in every moment, every embarrassment, these days. Art needs structure. Roth was more controlled. Cameras are placed at carefully chosen positions to capture powerful shots of this private world. The formal composition lends this intimate work grandeur, the sense of planning and order adding to the feeling of self-discipline in the face of disaster. It's what makes this such a harrowing encounter with the big things.

Who was Dieter Roth that his passing was so special? He was one of the most elusive and brilliant artists of the late 20th century. His works, the fragments of his sprawling creativity that can be seen in museums or tracked in private collections, include an old zinc bathtub filled with chocolate-covered busts of Beethoven; and an installation called Bar 2, a fully functioning bar complete with overflowing ashtrays.

Roth, from that generation of redemptive Germanic artists who emerged in the 1960s, looked at the stuff of modern life with a sarcastic, poetic eye. He kept diaries in which he worked out all his ideas and sketched out all his fantasies. In this exhibition, his diaries are shown as works of art in their own right, allowing us a glimpse into his reeky creative mind. One series of drawings seems to show his own head exploding into cosmic squiggles and monstrous caricatures. Another, sketched on a visit to Chicago, depicts his guardian angel.

Although an extraordinary draughtsman, Roth was not interested in turning that skill into something he could sell. His attitude to money, success and the consumer society is summed up in Flat Waste, his most stupefying diary of all. On rows of tidy shelves sit scores of files, each containing a month's worth of waste from his studio (anything that was less than 5mm thick). Plastic binders hold the detritus. Scrap paper. More scrap paper. A Gauloises cigarette pack. A Marlboro cigarette pack. Hotel stationary. A torn-up bill. The stuff of life, the stuff of death.

Few artists so fulfilled the great 20th-century tradition of art, begun with Dada, that spurns all self-indulgence, ultimately becoming identical to real life. The fact that he kept his beauty for his diaries, and rigorously avoided summing up his achievement in any saleable, elegant form, makes Roth, after his death, a monumental human archive – one that's just beginning to be opened up in this important, heartbreaking exhibition.

As an intense and inward artist from northern Europe, Roth would have warmed to the spooky fjords and winter suns in Van Gogh to Kandinsky: Symbolist Landscape, at the Scottish National Gallery (also part of the festival). In the late 19th century, artists began to look at the world through spectacles tinged absinthe green and suicidal black. Symbolism rejected outward appearances in favour of inner truth. The world is shown in shockingly subjective ways: mountains became nightmarish symbols of death, the sea a phantom.

This excellent survey excels at setting the titans of the age – Van Gogh, Gauguin, Munch, Monet – alongside the less well known and sometimes wickedly eccentric artists. With its radiating sea and sky captured in unreal colours, Albert Trachsel's The Island of Blossoming Trees (Dream Picture) looks like a psychedelic album cover, yet it was painted around 1912. And if you thought The Killing was an eerie journey into Scandinavian bleakness, take a look at Eugene Jansson's 1899 painting of Riddarfjärden: the Stockholm lake is transformed into a pool of midnight darkness strangely illuminated by phosphorescent sea creatures, with a horizon tinted blood-red.